Method of making semiconductor device

ABSTRACT

A semiconductor device is manufactured by a method including forming a first interlayer insulating film. A first etching stopper film is formed on the first interlayer insulating film. A conductive layer is formed on the first etching stopper film. A second etching stopper film is formed to cover the conductive layer, an upper surface of the conductive layer and both side surfaces of the conductive layer. A second interlayer insulating film is formed on the second etching stopper film. A hole is formed penetrating the second interlayer insulating film in a direction of thickness and reaching the conductive layer. An interconnect is formed in the hole. The step of forming a hole includes etching the second interlayer insulating film under a first etching condition, and etching the second etching stopper film under a second etching condition different from the first etching condition.

RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No.11/229,550, filed Sep. 20, 2005, now U.S. Pat. No. 7,301,237 claimingpriority of Japanese Application No. 2004-275565, filed Sep. 22, 2004,the entire contents of each of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device having aninterconnection connected to a conductive layer present above asemiconductor substrate as well as to a manufacturing method thereof

2. Description of the Background Art

Conventionally, a method of manufacturing a semiconductor deviceincluding the step of forming a hole penetrating a second interlayerinsulating film covering a conductive layer formed on a first interlayerinsulating film and reaching the conductive layer has been employed. Inthe method of manufacturing a semiconductor device, if a position atwhich the hole is formed is displaced from a position of the conductivelayer, the hole reaches the first interlayer insulating film under theconductive layer. Such penetration caused by misalignment of the hole ismore likely in a recent semiconductor device that has been reduced insize.

As a technique to prevent the hole from penetrating as far as the firstinsulating film under the conductive layer due to misalignment of thehole as described above, Japanese Patent Laying-Open No. 05-299515discloses a technique to provide an etching stopper film solely on asidewall of the conductive layer. In addition, Japanese PatentLaying-Open No. 2000-294631 discloses a technique to provide doubleetching stopper film in a damascene structure. Moreover, Japanese PatentLaying-Open No. 09-007970 discloses a technique to provide an etchingstopper film only on a lower side of the conductive layer.

None of the techniques described above, however, can completely solvethe problem of the hole reaching the first interlayer insulating film.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a semiconductor devicein which a hole reaching a conductive layer is prevented from reachingan interlayer insulating film provided under the conductive layer aswell as a manufacturing method thereof.

A semiconductor device according to the present invention includes afirst interlayer insulating film, a first etching stopper film formed onthe first interlayer insulating film, a conductive layer formed on thefirst etching stopper film, and a second etching stopper film formed atleast on the first etching stopper film. In addition, the semiconductordevice includes a second interlayer insulating film formed to cover thesecond etching stopper film and the conductive layer, and aninterconnection formed to penetrate the second interlayer insulatingfilm in a direction of thickness and to come in contact with theconductive layer.

According to the semiconductor device described above, a sandwichstructure in which the conductive layer is sandwiched by the firstetching stopper film and the second etching stopper film is formed.Therefore, when a method of manufacturing a semiconductor device whichwill be described later is employed, a hole reaching a first insulatinglayer, i.e., what is called hole penetration, can be prevented informing the hole in which an interconnection is embedded.

A method of manufacturing a semiconductor device according to thepresent invention includes the steps of forming a first interlayerinsulating film, forming a first etching stopper film on the firstinterlayer insulating film, and forming a conductive layer on the firstetching stopper film. In addition, the method of manufacturing asemiconductor device includes the steps of forming a second etchingstopper film to cover the first etching stopper film and the conductivelayer, forming a second interlayer insulating film on the second etchingstopper film, forming a hole penetrating the second interlayerinsulating film in a direction of thickness and reaching the conductivelayer, and forming an interconnection in the hole. The step of forming ahole includes the steps of etching the second interlayer insulating filmunder a first etching condition, and etching the second etching stopperfilm under a second etching condition different from the first etchingcondition.

Each of the first etching stopper film and the second etching stopperfilm described above may include any one of a silicon nitride film and asilicon rich oxide (SRO) film.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for illustrating a structure of a semiconductordevice according to an embodiment.

FIGS. 2 to 6 are diagrams illustrating a method of manufacturing asemiconductor device according to the embodiment.

FIGS. 7 and 8 are diagrams illustrating a method of manufacturing asemiconductor device according to a comparative example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A semiconductor device and a manufacturing method thereof according toan embodiment of the present invention will be described hereinafterwith reference to the drawings. Initially, a structure of thesemiconductor device according to the embodiment of the presentinvention will be described with reference to FIG. 1.

As shown in FIG. 1, the semiconductor device according to the presentembodiment includes an interlayer insulating film 1 provided above asemiconductor substrate. An etching stopper film 2 is formed oninterlayer insulating film 1. In addition, a conductive layer 3 isformed on etching stopper film 2. An etching stopper film 4 is formed tocover an upper surface of etching stopper film 2, one side surface ofconductive layer 3, and a part of an upper surface of conductive layer3. Furthermore, an interlayer insulating film 5 is formed to coveretching stopper film 4. An interconnection 8 penetrating interlayerinsulating film 5 in a direction of thickness and reaching conductivelayer 3 is formed.

According to the structure as above, when a hole in whichinterconnection 8 is embedded is formed, the hole does not reachinterlayer insulating film 1, although etching stopper film 2 ispartially etched. Consequently, reliability of the semiconductor deviceis improved.

A method of manufacturing the semiconductor device shown in FIG. 1 willbe described with reference to FIGS. 2 to 6.

Initially, interlayer insulating film 1 is formed above thesemiconductor substrate. Then, etching stopper film 2 is formed oninterlayer insulating film 1. Thereafter, conductive layer 3 is formedon etching stopper film 2. The structure shown in FIG. 2 is thusobtained.

As shown in FIG. 3, etching stopper film 4 is formed to cover etchingstopper film 2 and the upper surface and opposing side surfaces ofconductive layer 3. Then, interlayer insulating film 5 is formed tocover etching stopper film 4. Thereafter, a resist film 6 that has beenpatterned to form a hole reaching conductive layer 3 is formed. Thestructure shown in FIG. 4 is thus obtained.

Then, as shown in FIG. 5, using resist film 6 as an etching mask,interlayer insulating film 5 is etched to expose etching stopper film 4.Then, etching stopper film 4 is etched under an etching conditiondifferent from that for etching interlayer insulating film 5. As shownin FIG. 6, a hole 7 reaching conductive layer 3 is thus formed.Conductive layer 3 is exposed on a bottom surface of hole 7.

Here, consider a case in which hole 7 is displaced from a position ofconductive layer 3 and etching stopper film 4 is removed to expose oneof opposing side surfaces of conductive layer 3, as shown in FIG. 6.Even in such a case, as etching stopper film 2 is provided under etchingstopper film 4, the bottom surface of hole 7 does not reach interlayerinsulating film 1, although the bottom surface of hole 7 penetratesetching stopper film 4 and reaches etching stopper film 2.

According to the method of manufacturing a semiconductor deviceaccording to the present embodiment as above, in a state where twoetching stopper films sandwiching conductive layer 3 from above andbelow are provided, interlayer insulating film 5 present aboveconductive layer 3 is initially etched. Thereafter, etching stopper film4 present on conductive layer 3 is removed. Therefore, such adisadvantage as hole 7 reaching interlayer insulating film 1 isprevented. Consequently, reliability of the semiconductor device isimproved.

Here, etching stopper film 2 has a film thickness of approximately 20 nmto 200 nm. Conductive layer 3 is implemented by a film consisting oftungsten, aluminum or the like and has a thickness of approximately 200nm. Meanwhile, etching stopper film 4 has a film thickness of 50 nm.Etching of interlayer insulating film 5 described above is carried outby dry etching such as RIE (Reactive Ion Etching). Desirably, an Si-richinsulating film having a composition ratio of O/Si of approximately 1.2,that is, an SRO (Silicon Rich Oxide) film, is employed as etchingstopper films 2 and 4. Alternatively, etching stopper films 2 and 4 maybe implemented by a silicon nitride film.

A gas obtained by adding at least any one of O₂ and CO or Ar to a gassuch as C₄F₈, C₅F₈, C₄F₆, C₂F₄, or C₃F₆ representing a CF-based gascontaining C and F is basically employed as an etching gas for the firstetching condition of the present invention. As shown in FIG. 5, with theuse of this gas, interlayer insulating film 5 (silicon oxide film) isinitially etched. The etching gas described above is merely an exampleof gases that can selectively etch interlayer insulating film 5 withrespect to etching stopper film 4, and the gas for etching interlayerinsulating film 5 is not limited to those described above.

In addition, a gas obtained by adding at least any one of O₂ and CO orAr to a gas such as CHF₃ or CH₂F₂ containing C, F and H is employed asan etching gas for the second etching condition of the presentinvention. As shown in FIG. 6, with the use of this gas, exposed etchingstopper film 4 is etched. Consequently, conductive layer 3 is exposed onthe bottom surface of hole 7. The etching gas described above is merelyan example of gases for efficient etching of etching stopper film 4, andthe etching gas for etching stopper film 4 is not limited to thosedescribed above.

Semiconductor devices structured as shown in FIGS. 7 and 8 areconsidered as comparative examples of the semiconductor devicestructured according to the embodiment of the present invention asabove.

In FIG. 7, etching stopper film 4 on conductive layer 3 is provided,however, etching stopper film 2 under conductive layer 3 is notprovided. With such a structure, after interlayer insulating film 5 isetched, etching stopper film 4 should be etched under a differentetching condition, so as to expose conductive layer 3. Here, if aposition at which hole 7 is formed is displaced from an end portion ofconductive layer 3, the bottom surface of hole 7 penetrates etchingstopper film 4, to reach interlayer insulating film 1.

In FIG. 8, etching stopper film 2 under conductive layer 3 is provided,however, etching stopper film 4 on conductive layer 3 is not provided.With such a structure, when interlayer insulating film 5 is etched toexpose conductive layer 3, it is difficult to stop etching at the timingof exposure of conductive layer 3, because a distance in a direction ofthickness of interlayer insulating film 5 is great. Accordingly,particularly if a position at which hole 7 is formed is displaced froman end portion of conductive layer 3 by a small amount of not largerthan 20 nm, the bottom surface of hole 7 penetrates etching stopper film2, to reach interlayer insulating film 1.

As can been seen from comparison between the structure according to thecomparative examples in FIGS. 7 and 8 and the structure according to thepresent embodiment shown in FIGS. 1 to 6, penetration of hole 7 as faras interlayer insulating film 1 can effectively be prevented byproviding etching stopper films 2 and 4 sandwiching conductive layer 3from above and from below.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

1. A method of manufacturing a semiconductor device, comprising thesteps of: forming a first interlayer insulating film; forming a firstetching stopper film on said first interlayer insulating film; forming aconductive layer on said first etching stopper film; forming a secondetching stopper film to cover said first etching stopper film, an uppersurface of said conductive layer and both side surfaces of saidconductive layer; forming a second interlayer insulating film on saidsecond etching stopper film; forming a hole penetrating said secondinterlayer insulating film in a direction of thickness and reaching saidconductive layer; and forming an interconnection in said hole; whereinsaid step of forming a hole includes the steps of etching said secondinterlayer insulating film under a first etching condition, and etchingsaid second etching stopper film under a second etching conditiondifferent from said first etching condition.
 2. The method ofmanufacturing a semiconductor device according to claim 1, wherein eachof said first etching stopper film and said second etching stopper filmincludes any one of a silicon nitride film and a silicon rich oxide(SRO) film.